I went through the public system having blood tests, bone marrow biopsies, psychological tests, cat scans and MRI tests. They all came back negative. The doctors said they couldn't find out what was wrong with me. It was only that we pushed for a SPECT test that finally showed the severe damage in my brain that was causing the dementia.
t took 3 years to finally get that done and it showed Lewy Body Dementia. Because I was so young the doctors didn't entertain that I even had something like a degenerative brain disease as the cause of my dementia. If I had this test early on I could have saved 3 years going from doctor to doctor and hospital to hospital.
If you're a younger person who's gone through a similar plight as mine, don't give up. Push for a SPECT test...it may be the thing that finally gives you some answers.